Pump arrangement

ABSTRACT

The subject matter of the present invention is a pump arrangement, in particular for use in the body&#39;s own vessels, having a pump and a sheath receiving the pump, bounding a flow passage and having a distal intake opening and a proximal outflow opening for producing a driving flow by means of the pump, wherein the pump is arranged in a first fluid-tight section having the distal intake opening and a second fluid-tight section includes the proximal outflow opening. In accordance with the invention, a further inlet opening is present between the first section, and the second section and is arranged between the intake opening and the outflow opening, with the first section and the second section being arranged with respect to one another such that the inlet opening opens into the flow proximal to the pump.

BACKGROUND OF THE INVENTION

The invention is in the field of mechanical engineering and finemechanics and can in particular advantageously be used in the medicalarea.

In this respect, the subject matter is a pump arrangement in accordancewith the preamble of claim 1.

Pump arrangements are increasingly known from prior art in particularfor use in the body's own vessels. Said pumps can be used, for example,for short-term cardiac support to relieve the cardiac muscle of apatient after a cardiogenic shock (myocardial infaction). In thisprocess, use is sometimes made of transfemorally implanted micro-axialpumps.

Such a pump arrangement is known, for example, from EP 2 047 872 A1. Thepump arrangement disclosed there includes a pump, a sheath receiving thepump and having a distal intake opening and a proximal outflow opening,with the pump generating a driving flow in operation from the distalintake opening toward the proximal outflow opening. A flow passage thusextends between the intake opening and the outflow opening. The pump isin this respect arranged in a first fluid-tight section of the sheathwhich has the distal intake opening and which is formed as a PU coveringof a housing. Furthermore, a second fluid-tight section of the sheath ispresent which includes the proximal outflow opening and is formed as anoutflow hose. The outflow hose is connected with material continuity tothe PU covering. The pump arrangement is arranged such that the pumpformed as a rotor can, for example, be arranged in a ventricle, with theoutflow hose extending from the ventricle into the aorta.

All the blood entering into the aorta via outflow openings of theoutflow hose moves through the intake opening into the flow passageformed by the sheath and in so doing passes through the rotor. In otherwords: The conveyed flow conveyed by the pump is identical to the totalflow exiting at the outflow opening.

The subject matters of documents DE 41 24 299 A1, DE 10 2004 054 714 A1,WO 2007/112033 A2 and US 2008/132748 A1 also work in accordance with theaforesaid principle.

Since all blood comes into direct contact with the pump, a particularlyhigh effort is required in the manufacture of the pump to reduce theblood-damaging effect of the moving pump parts. This blood-damagingeffect is manifested in direct mechanical shear at moving and stationarypump parts and in shear by shear stress fields occurring in the fluidwhile passing through the flow passage (see above). Pump geometriestherefore also arise which cannot be used by means of a minimallyinvasive procedure.

BRIEF SUMMARY OF THE INVENTION

It is the underlying object of the present invention to reduce thedanger of damage to the blood or to the fluid transported through thepump. Special attention must be paid to the choice of the materials inthe medical use of the following pump arrangement(s). Said materialsshould meaningfully satisfy the demands of biocompatibility.Interactions with foreign-body surfaces form the third big aspect, inaddition to the above implementation, in blood damage and have beensufficiently examined for some time.

In accordance with the invention, a further inlet opening is introducedbetween the first section and the second section with the first sectionand the second section being arranged with respect to one another suchthat the inlet opening opens into the flow passage proximal thecompressible pump. In this respect, the further inlet opening can alsobe formed as an inlet passage which has its inlet opening distal of orproximal to the pump or also at the level of the pump, but which onlyopens into the flow passage proximal to the pump.

It is possible with the aid of the feature in accordance with theinvention that a driving flow running through the pump flows through theflow passage past the opening of the inlet opening in the direction ofthe outlet opening and thus effects a pressure drop with respect to thefluid pressure present in the inlet opening which results in a pullingof fluid through the inlet opening and into the flow passage. The totalflow outflowing at the outflow opening is hereby larger than the drivingflow directly passing through the pump and conveyed thereby since anadditional intake flow is added through the inlet flow.

The intake flow arises in that a suction effect arises due to thedriving flow such as also occurs in some kinds of turbine or water jetpumps. On the suction effect, an impulse is transmitted from the drivingflow to the intake flow by friction or viscosity or turbulent mixing ofthe fluid. In this manner, viscous, turbulent shear stresses arise. Theimpulse direction of the propellant flow is transmitted to particlesfrom the medium of the intake flow to be conveyed which are transportedinto a zone downstream within the sheath.

Substantially, the principle of a jet pump is realized with the aid ofthe feature in accordance with the invention, with the driving flowdirectly passing through the pump and conveyed thereby carrying along anintake flow entering through the further inlet opening.

The inlet opening in this respect extends between the first section andthe second section, with the entry to the inlet opening being able to beproximal to or distal of the pump, with it being advantageous if theentry is distal of the outflow opening. Only the opening of the inletopening into the flow passage should be proximal the pump so that thesuction effect which is caused by the driving flow is utilized well.

A compressible pump is understood as a preferably radially compressiblepump or pump arrangement. In this respect, the pump or the first sectionand/or the second section and/or the housing and/or the rotor are formedsuch that the pump can be conducted to the target site in a catheter,with the catheter having an inner diameter which is smaller than thefirst section and second section or the housing in the unfoldedcondition. Such pumps or pump arrangements are known, for example, in EP2 047 872 A1, in WO 2010/063494 A1, in U.S. 61/120,095 or in WO2010/127871 and in U.S. 61/175,519 A1.

An inlet opening formed between the intake opening and the outflowopening is particularly advantageous.

The first section and the second section of the sheath can be formed inone piece or as components separate from one another.

In a first embodiment, the cross-section of the proximal end of thefirst section is smaller than the cross-section of the distal end of thesecond section. The conveyed flow is hereby concentrated onto an area ofthe cross-section of the proximal end of the first section and can takealong further medium on entry into the second section, said medium beingable to flow in at least through accesses in the region of the remainingarea of the cross-section of the distal end of the second section.

In a further embodiment, the cross-section of the first sectionconverges toward its proximal end. Due to this convergence, the firstsection is of nozzle form at its proximal end. This results in animprovement in the efficiency and thus in an increase in the sucked-inintake flow. In addition, the feature helps effect a reduction in thetotal pump arrangement.

In a further embodiment, the distal end of the second section and theproximal end of the first section overlap, i.e. the distal end of thesecond section is further distal than the proximal end of the firstsection. In this respect, it is advantageous if the inlet openingbetween the first section and the second section is in each case formedas an intake passage or in the manner of a passage from the distal endof the second section toward the proximal end of the first section. Theintake flow hereby preferably flows almost coaxially to the conveyeddirection of the driving flow through the intake passage into the flowpassage in the direction of the outflow opening. In this respect, animpulse of the driving flow in the direction of the outflow opening isalready transmitted to the intake flow due to the main axis of theintake passage which is preferably directed in the direction of theconveyed flow. This results in an improvement in efficiency.

In a further embodiment, the distal end of the second section is furtherproximal than or at the same level as the proximal end of the firstsection. Due to the spacing, the concentrated driving flow exiting theproximal end of the first section is incident onto a fluid of differentpressure and different directions so that the concentrated conveyedflow, like a fluid of higher density, flows on into the start of thesecond section defined by the distal end of the second section and takesalong fluid which is located between the first section and the secondsection. The total flow hereby becomes larger with respect to thedriving flow passing through the pump. In this respect, care must,however, be taken that the spacing between the distal end of the secondsection and the proximal end of the first section is kept small in ordernot to effect any dispersion of the conveyed flow with respect to theflow present outside the sheath. The spacing should be approximatelyfrom 0 to ¼ of the diameter of the proximal outlet opening of the firstsection.

In a further embodiment, the second section includes at least onepartial region made from a flexible material. It is hereby possible thata second section which is disposed between, for example, a ventricle anda blood vessel, with the ventricle and the blood vessel being connectedby means of a valve closing and opening rhythmically, can be pressedthrough the valve and the fluid is thus conveyed in turn with therhythmic movement of the valve. PU, PE, PP, silicone or Parylene are,for example suited as suitable materials provided that they satisfy themechanical and geometrical demands and the demands on biocompatibility.

In a further embodiment, the pump arrangement has a housing receivingthe pump. This is in particular suitable when the pump is a compressiblepump which is conveyed to its working site by means of a cathetertogether with the housing. In addition, the housing gives the pumparrangement additional stability. The housing can, for example, bemanufactured from Nitinol.

On the presence of a housing, the first section can be made as a jacketof the housing or as a coating of the housing, with only a partialregion of the housing, preferably an axial partial region, having tohave a fluid-tight jacketing or coating. Materials are suitable ascoatings or jacketings here such as were already named in thedescription of the second section made from a flexible material.

In a further embodiment, the housing has a constriction and/or a bulgeproximal to the pump. In this respect, a constriction is to beunderstood as a convergence of the cross-section of the housing withrespect to the region of housing receiving the pump. A bulge has across-section of the housing enlarged with respect to a constriction orwith respect to the region receiving the pump. Converging portions ofthe first section or lager cross-sections of the second section can beimplemented in a particularly easy and advantageous manner with the aidof such a shape. The second section can also be connected to thehousing.

In a further embodiment, the first section and the second section areconnected to one another with material continuity or are preferablyformed in one piece.

In a further embodiment, the second section is formed as an outflowhose.

In a further embodiment, the first section, the second section or anyhousing includes support elements such as a support ring, plasticthreads, wires, connecting struts or a preferably compressible sleevefor spacing apart the first section and the second section so that anintake flow flowing through the inlet opening does not have the resultthat a surface of the second section is sucked onto the surface of thefirst section and thus interrupts the intake flow or to ensure that thefurther inlet opening is permanently open in pump operation. The supportelements are in this respect connected to the first section or to thesecond section such that they are compressible together with the pump.This can be achieved, for example, via flexible support elements orsupport elements made from hyper elastic materials or support elementsmade from memory materials such as Nitinol.

The second section can furthermore have a support ring in the region ofthe inlet opening, said support ring ensuring a spacing of the firstsection from the second section in the region of the inlet opening sothat an intake flow flowing through the inlet opening does not have theresult that a surface of the second section is sucked onto the surfaceof the first section and thus interrupts the intake flow. This is inparticular advantageous when the second section is a section made fromflexible material such as an outflow hose.

In a further embodiment, the second section has a sleeve which includesthe further inlet apparatus or partly includes the further inletopening. Said sleeve can be connected as an additional special part, forexample, to a flexible region of the second section. In this respect, itis advantageous if the sleeve is of stable shape and thus forms asuitable resistance with respect to the fluid in the working state whichis defined, for example, by an unfolding of the pump arrangement at itswork site in the body so that the intake flow is channeled by the sleeveand flows into the flow passage.

Instead of a sleeve, a further hose section or a tube can also be used.

In a further embodiment, the pump is a compressible pump, which resultsin a lighter introduction of the pump into the bloodstream or into avessel.

It is furthermore advantageous if the pump is an axial flow pump whichis fastened on a rotatable shaft which drives the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in the following in more detail withreference to some embodiments. There are shown:

FIG. 1 the use of a pump arrangement in a heart;

FIG. 2 a schematic representation of an embodiment of the pumparrangement;

FIG. 3 a schematic representation of an inlet opening of an embodimentof the pump arrangement;

FIG. 4 an embodiment of a pump arrangement;

FIG. 5a a further embodiment of a pump arrangement;

FIG. 5b a schematic representation of the pump arrangement of FIG. 5 a;

FIG. 6 a further embodiment of a pump arrangement;

FIG. 7 a further embodiment of a pump arrangement; and

FIGS. 8a-8c cross-sections through different pump arrangements.

DETAILED DESCRIPTION OF THE INVENTION

A possible use for the pump arrangement 1 is shown in FIG. 1. The pumparrangement 1 includes an elongate catheter which extends through theblood vessel 2 and in which a shaft extends which drives the pumppresent in the pump arrangement 1 and formed as a rotor. The proximalend of the pump arrangement (viewed without the catheter) is located inthe blood vessel 2, whereas the distal end of the pump arrangement 1including the pump is located in the ventricle 3. The blood vessel 2 isbounded by the vessel wall 4. The valve 5 which opens and closesrhythmically furthermore bounds the ventricle 3 and enables the bloodflow from the ventricle 3 into the blood vessel 2.

Further uses are possible in addition to the shown use of a pumparrangement in accordance with the information. The pump can thus, forexample, be used in a different vessel of the body to increase theconveying performance.

The mode of operation of a pump arrangement in accordance with theinvention should be explained with reference to FIG. 2. The pumparrangement 10 includes a pump 11 which is formed as a rotor. The pump11 is set into rotation by means of a shaft which is shown, but notnumbered and can thus transport a driving flow Q_(T). The pumparrangement 10 has a sheath 12 which includes a first section 12 a and asecond section 12 b. An intake opening 13 is located in the firstsection 12 a through which intake opening a fluid can enter into thelumen of the first section 12 a, is sucked in by the pump 11 and istransported as a driving flow Q_(T) in the direction of the outflowopening 14. The sheath 11 defines the flow passage S between the intakeopening 13 and the outflow opening 14, said flow passage completelyincluding the lumen of the first section 12 a and partially including alumen of the second section 12 b.

The first section and the second section overlap between the proximalend of the first section 12 a and the distal end of the second section12 b. An inlet opening 15 is defined by the overlap through which thefluid can enter into the flow passage S from a region outside the lumenof the first section 12 a. A pressure drop occurs in the region 17 inthe region of the proximal end of the first section 16 due to thedriving flow Q_(T) conveyed by the pump. This is shown in FIG. 3.

Further fluid is sucked through the inlet opening 15 in the direction ofthe outflow opening 14 due to the pressure drop in the region 17 andenters into the flow passage as the intake flow Q_(S) proximal to theproximal end of the first section 16.

The first section 12 a and the second section 12 b both include a lumen.In this respect, the lumen of the first section 12 a has across-sectional area A₁; the lumen of the second section 12 b has across-sectional area A₂. In the present embodiment, the cross-sectionsA₁ and A₂ remain the same over the total length of the respectivesection; however, this is not a compulsory feature. The intake flowalready receives an impulse direction in the direction of the outflowopening 14 due to the passage extending parallel to the driving flowbetween the distal end of the second section 12 b and the proximal endof the first section 12 a and formed as an inlet opening 15. The volumeper time Q_(A) which has flowed out at the outflow opening 14 is largerdue to the additional intake flow Q_(S) than the driving flow Q_(T)passing through the pump.

A further embodiment of a pump arrangement is described in FIG. 4. Thepump arrangement 20 is located in a blood vessel which is bounded by thevessel walls 4. The distal end of the pump arrangement 20 is locateddistal of the valve 5; the proximal end is located proximal to the valve5.

The pump arrangement 20 includes a compressible rotor 21 which isfastened to the shaft 22 at one side. The bearing is located at theproximal end of the rotor. The rotor 21 is surrounded by a housing 23which can be manufactured from Nitinol. The housing comprises individualthreads, wires or struts of Nitinol which mutually cross and produce adiamond pattern. The fluid can pass through the diamonds and so reachthe rotor 21.

The housing 23 is partly covered by a jacketing 24 in a fluid-tightmanner. In this respect, the jacketing 24 extends over a length L₂₄ sothat a driving flow Q_(T) driven by the rotor is bundled and exits thehousing 23 at the proximal end of the jacketing 24 and flows in thedirection of the outflow openings 29 which are arranged in an outflowhose 25.

The jacketing 24 in the embodiment of the pump arrangement 20 forms thefirst section of the sheath; the outflow hose 25 forms the secondsection of the sheath. The distal end of the outflow hose is fastened tothe housing 23 and is further distal than the proximal end of the sheath24.

The sheath 34 converges from the region of the rotor 21 in the proximaldirection. The lumen formed by the sheath 24 thus has a cross-sectionalarea A_(1D) in the region of the rotor 21 which is larger than thecross-sectional area A_(1P) of the proximal end of the sheath 24. Anozzle effect is hereby produced which accelerates the driving flowQ_(T) in accordance with the principle of the Venturi tube so that itflows in the direction of the outflow openings 29 at a higher flow speedat the proximal end of the sheath 24. The intake passage 26 which isaccessible through the inlets 27 is located between the sheath 24 andthe outflow hose 25. It can be recognized from FIG. 4 that a pluralityof inlets 27 are present, with the inlets being designed as circularsections of the outflow hose in the region of its distal end. Due to thereduced pressure in the region of the exiting driving flow Q_(T) anintake flow Q_(S) is sucked through the inlet 27 and the intake passage26 and flows into the flow passage S, which transports the totalconveyed flow to the outflow openings 29.

A support ring 28 which is stable in shape in the working state of thepump is located radially peripherally proximal to the inlets 27 and theoutflow hose 25. A suction of the surface of the outflow hose 25 to thesheath 24 due to the occurring intake flow is thus prevented. The intakepassage 26 thus remains open and further fluid is sucked through theintake passage 26, caused by the driving flow Q_(T), into the flowpassage S.

A further embodiment of the pump arrangement in accordance with theinvention is shown in FIG. 5a . The pump arrangement 30 includes a rotor31 which is supported at both sides, i.e. distal and proximal, at anaxle 32. The rotor 31 is arranged in a housing 33 which is sectionallyjacketed by a PU coating 34. The PU coating 34 in this respect extendsover a length L₃₄ up to a region disposed proximal to the proximal endof the rotor 31. The housing 33 has a constriction 33 a and expandsproximal of the constriction 33 a to form a bulge 33 b. In the region ofthe bulge 33 b, the outflow hose 35 is connected to the housing 33 withmaterial continuity. The bulge 33 b and the constriction 33 a are spacedapart from one another, measured along the axis 32, by a spacing d whichamounts to around 0 to ¼ of the diameter of the constriction 33 a. Inthis respect, the spacing d is selected so that due to the driving flowQ_(T) exiting the proximal end of the PU coating 34 and driven by therotor 31, an intake flow Q_(S) is sucked in through the inlet opening 36resulting between the PU coating 34 and the outflow hose 35. The drivingflow Q_(T) exiting the jacketing is flowed out at a pressure P₁. Apressure P₂ applies outside the jacketing 34 which is lower than thepressure P₁. An intake flow Q_(S) is sucked into the inlet opening 36due to this pressure difference and is transported through the outflowhose toward the outflow opening 39 where it is expelled as a totalcurrent Q_(A) at a pressure P₃ which is greater than the pressure P₂.The total flow Q_(A) is in this respect lower than the driving flowQ_(T).

Even if the flow passage S, which extends between the intake openingdistal of the rotor 31 and the outflow opening 39, is permeable forfluid between the proximal end of the PU coating 34 and the distal endof the outflow hose 35, the inflow opening 36 nevertheless opens intothe flow passage which is defined by the flow course of the drivingflow. If the driving flow is correspondingly high, it enters practicallydirectly into the outflow hose.

It is possible due to the inlet opening present in addition to theintake opening disposed distal of the rotor 31 that a partial flow ofthe total flow Q_(A) exiting at the outflow opening 39 does not pass therotor 31 and there is thus no risk of blood damage by the rotor 31.

The embodiment of the pump arrangement 30 of FIG. 5a is shown againschematically in FIG. 5b . It can be recognized here that the distal endof the PU coating 34 has a cross-sectional area A_(1D) which is largerwith respect to the cross-sectional area A_(1P) which is present at theproximal end of the PU coating 34. The lumen surrounded by the PUcoating 34 thus converges, which has the consequence of an efficiencyimprovement. The cross-sectional area A_(2D) of the lumen of the outflowhose 35 is in turn larger than the cross-sectional area A_(1P). An inletopening 36 is thus defined at least by the region of the cross-sectionalarea A_(2D) which remains after the subtraction of the cross-sectionalarea A_(1P). Said inlet opening in turn opens into the flow passage S.

A further embodiment of a pump arrangement is shown in FIG. 6. In thisrespect, a detailed description of the axle and of the pump drive isdispensed with. The pump arrangement 40 includes a rotor 41 as well as afirst section 42 a and a second section 42 b of a sheath. The intakeopening 43 which supplies fluid to the pump 41 is located at the distalend of the first section 42 a. The fluid supplied to the pump 41 isaccelerated and is expelled as a driving flow Q_(T) at the proximal endof the first section 42 a. The second section 42 b is composed of aflexible region 420 b which is connected to a compressible sleeve 421 bwhich is of stable shape and is rigid in the working state of the rotor.The compressible sleeve 421 b is connected to the first section 42 a bymeans of plastic threads or wires 422 b. The cross-section extending inconverging manner from the distal end of the sleeve 421 b to theproximal end of the sleeve 421 b has the effect in conjunction with thedriving flow Q_(T) of sucking in an intake flow Q_(S) through the inletopening 45 which is formed between the sleeve 421 b and the firstsection 42 a, with the intake flow Q_(S) being combined with the drivingflow Q_(T) and, in the flow passage S, flowing out of the outflowopening 44 as the total flow Q_(A). It is in turn obvious from FIG. 6that the inlet opening 45 opens into the flow passage S.

A further embodiment of a pump arrangement is shown in FIG. 7. The pumparrangement 50 includes a pump 51 which is formed as an axial-flow pumphaving a rotor. Furthermore, a sheath 52 is present which can be dividedinto a first section 52 a and into a second section 52 b. In thisrespect, the first section and the second section are connected to oneanother with material continuity or are manufactured in one piece. Anintake opening 53, which supplies fluid to the rotor, is located at thedistal end of the sheath 52 so that a driving flow Q_(T) is conveyed inthe working state of the rotor. The driving flow Q_(T) is conveyed inthe direction of the outflow opening 54. An inlet opening 55 throughwhich an intake flow Q_(S) effected by the driving flow Q_(T) can enterinto the flow passage S defined by the sheath 52 is located between thefirst section 52 a and the second section 52 b. The special feature ofthis embodiment is that the sheath 52 is made in one piece, in contrastto the previously shown embodiments in which the first sectionrepresents a separate component with respect to the second section.

Some different geometries of entries of the inlet openings should beshown with respect to FIGS. 8a -c.

A cross-section of the embodiment of FIG. 6 is shown in FIG. 8a . Whatcan be seen is the intake opening 543 with a cross-sectional areaA_(1P). Disposed proximal thereto, i.e. further into the plane of thedrawing, the sleeve 421 b is located with the cross section A_(2D)measured at its widest periphery. The plastic threads 422 b connect thesleeve 421 b to the first section 42 a.

The embodiment of FIG. 5a is shown in FIG. 8b . The intake opening 33can be recognized which is defined by the PU coating 34. The PU coating34 simultaneously defines a lumen which has a cross-sectional areaA_(1P) in the region of the rotor. In addition, the axle 32 can berecognized at the center of the intake opening 33. Proximal to the rotor(cf. FIG. 5a ), the housing 33 which is formed by threads, wires orstruts of Nitinol converges to a cross-sectional area A_(1P) which isdefined by the constriction 33 a. At proximal, the housing 33 widens toform a bulge 33 b, with the outflow hose 35 being connected to thehousing in the region of the bulge. It can clearly be recognized withreference to the representation shown in FIG. 8b that the region 36disposed between the outflow whose 35 and the PU coating 34 serves as aninlet opening for an intake flow.

In FIG. 8c , the embodiment of FIG. 4 is shown. In this respect, thecross-section is shown at the level of the support ring 28. The lumendefined by the jacketing 24 of the first section and having thecross-sectional area A_(1D) can be recognized. The intake passage 26through which additional fluid is sucked in, driven by the driving flowrunning through the lumen of the jacketing 24 in the proximal direction,is located between the jacketing 24 and the outflow hose 25. The outflowhose 25 has a cross-sectional area of A_(2D) in this region. The supportring 28 can clearly be recognized, as can the connection struts 28 awhich connect the support ring to the jacketing 24. The support ring iscomposed of a plurality of segments 28 b which can be brought into afolded state for introduction of the pump arrangement with the aid of acatheter.

REFERENCE NUMERAL LIST

-   1, 10, 20, 30, 40, 50 pump arrangement-   2 blood vessel-   3 ventricle-   4 vessel wall-   5 heart valve-   6 vessel valve-   11, 41, 51 pump-   12, 42, 52 sheath-   12 a, 42 a, 52 a 1st section of the sheath-   12 b, 42 b, 52 b 2nd section of the sheath-   13, 43, 53 intake opening-   14, 44, 54 outflow opening-   15 inlet opening-   16 proximal end of the 1st section-   17 region of pressure drop-   21, 31 rotor-   22, 32 axle-   23, 33 housing-   24, 34 jacketing-   L24, −L34 length of the jacketing-   25, 35, 420 b outflow hose-   26, 36 intake passage-   27 inlets-   28 support ring/spacer-   33 a constriction-   33 b bulge-   421 b sleeve-   422 b spacer-   Q_(T) conveyed flow-   Q_(S) intake flow-   Q_(A) total flow-   A₁, A₂, A_(1D), A_(1P), A_(2D), cross-section

The invention claimed is:
 1. A pump arrangement, comprising: acompressible rotor configured for use within a blood vessel; a sheathreceiving the compressible rotor, the sheath bounding a flow passage andhaving a distal intake opening and a proximal outflow opening, thesheath comprising a first fluid-tight section including the distalintake opening and a second fluid-tight section including the proximaloutflow opening, the compressible rotor being arranged in the firstfluid-tight section, the second fluid-tight section enclosing at least aportion of the first fluid-tight section; and an inlet opening disposedbetween the first fluid-tight section and the second fluid-tightsection, the first fluid-tight section and the second fluid-tightsection being arranged such that the inlet opening opens into the flowpassage proximal to the compressible rotor.
 2. The pump arrangement inaccordance with claim 1, wherein the cross-section of the proximal endof the first fluid-tight section is smaller than the cross-section ofthe distal end of the second fluid-tight section.
 3. The pumparrangement in accordance with claim 2, wherein the cross-section of thefirst fluid-tight section converges toward its proximal end.
 4. The pumparrangement in accordance with claim 3, wherein the inlet opening isformed as an intake passage extending between the first fluid-tightsection and the second fluid-tight section.
 5. The pump arrangement inaccordance with claim 1, wherein the second fluid-tight section includesa region made from a flexible material.
 6. The pump arrangement inaccordance with claim 5, wherein the first fluid-tight section is ajacketing of a pump housing that surrounds the compressible rotor. 7.The pump arrangement in accordance with claim 6, wherein the secondfluid-tight section is connected to the pump housing.
 8. The pumparrangement in accordance with claim 7, wherein the first fluid-tightsection and the second fluid-tight section are connected to one anotherwith material continuity.
 9. The pump arrangement in accordance withclaim 8, wherein the second fluid-tight section includes an outflowhose.
 10. The pump arrangement in accordance with claim 9, wherein thefirst fluid-tight section or the second fluid-tight section has supportelements for spacing the first fluid-tight section and the secondfluid-tight section.
 11. The pump arrangement in accordance with claim10, wherein the second fluid-tight section has a support ring in theregion of the inlet opening.
 12. The pump arrangement in accordance withclaim 11, wherein the second fluid-tight section includes a sleeveincluding the further inlet opening.
 13. The pump arrangement inaccordance with claim 12, wherein a rotatable shaft is present on whichthe compressible rotor is arranged.